ICP-OES测定磷系阻燃纤维中磷含量的方法

采用H2SO4-HNO3湿法灰化法消解、电感耦合等离子体发射光谱仪(ICP-OES)测定磷系阻燃纤维的磷含量,确定了实验测定的最佳条件。结果表明:方法的检出限为0.00402 mg/L,回收率为94.5%～94.7%,相对标准偏差在2%以内。该法具有操作简单,所需试剂较少,快速,检出限低,精密度高,准确度高的特点,具有良好的应用前景。     

微波消解法测定小麦胚芽中磷的含量

用微波消解技术对小麦胚芽进行前处理,然后用磷钼蓝分光光度法测定了其磷含量。使用微波消解炉,实验结果表明:该法操作简单、试剂用量少、重现性好,用微波消解技术大大缩短了样品前处理的时间,适于食品中磷元素含量的测定。     

小麦胚芽中磷含量的快速测定

用微波消解技术对小麦胚芽进行前处理,然后用磷钼蓝分光光度法测定了其磷含量.使用微波消解炉,实验结果表明:该法操作简单、试剂用量少、重现性好,用微波消解技术大大缩短了样品前处理的时间,适于食品中磷元素含量的测定.     

钒钼黄分光光度法检测液态特殊食品中磷含量的优化

目的建立钒钼黄分光光度法检测低磷含量液态婴幼儿配方食品、液态特殊医学用途配方食品等特殊食品中磷含量的分析方法。方法试样经消解,磷在酸性条件下与钒钼酸铵生成黄色络合物钒钼黄,于440 nm测定试样溶液中钒钼黄的吸光度值,幵与标准系列比较定量。对3种基质液态特殊食品的磷含量进行测定。结果增大称样量能满足方法准确度和精密度要求;称样量为4 g时,回收率范围为92.4%～107.0%,相对标准偏差为0.8%～3.7%;方法定量限为30 mg/100 g。结论该方法能够准确测定液态配方食品中较低含量的磷,适合液态婴幼儿配方食品、液态特殊医学用途配方食品等特殊食品中磷含量的测定。     

磷钼蓝分光光度法测定果蔬中有机磷农药

将磷钼蓝分光光度法中的还原剂改进为苯酚,采用苯酚还原磷钼蓝分光光度法测定果蔬中的总磷、无机磷,从而得出有机磷含量。实验表明,该方法最大吸收波长为810nm,磷含量在0～40μg范围内,符合比耳定律,标准曲线的回归方程为y=0.0161x＋0.0008,相关系数R2=0.9965,表观摩尔吸收系数为2.8×105L.mol-.1cm-1,与标准法相比,相对偏差为2.21%～4.47%,回收率在93.10%～102.26%之间。     

磷系共聚阻燃聚酯切片的研制及其性能

本文选用磷系共聚阻燃剂研制开发共聚阻燃聚酯切片，并就阻燃聚酯切片的一些性能进行了初步讨论。     

微波消解-分光光度法测定小桐子毛油中的磷含量

采用微波消解技术对小桐子毛油进行预处理,通过分光光度法测定其中磷的舍量。选取了适宜的微波消解条件。分析了方法的精密度,与干法消解测定结果进行了对比,并开展了样品加标回收率试验。结果表明:该法操作简单、试剂用量少、重现性好,用微波消解技术大大缩短了样品前处理的时间,适于小桐子毛油中磷含量的快速分析。     

磷酸酯表面活性剂中微量无机磷的实时测定

利用磷钼酸蓝离心分光光度法,对磷酸酯表面活性剂中的微量无机磷进行直接测定,该方法在大量有机磷酸酯存在时对无机磷的测定无干扰,样品无需预处理,回收率为95%～103%.可监测反应釜中的磷化剂含量,适用于对生产过程的实时监控.     

食品中磷测定方法的改进

对食品中磷的测定方法进行改进和完善,研究出新的检测方法。使用微波消解仪,在食品中加入硝酸密闭消解,并用抗坏血酸代替国标方法中的对苯二酚,同钼酸铵、亚硝酸钠溶液与消解液反应,用钼蓝反光光度法在660 nm波长处测定样品中磷的含量。结果表明,该方法可以将样品消解完全,磷的含量与吸光度呈线性关系,相关系数为0.999 8,对样品的加标回收率为95.4%~105.0%,本方法与国标法测定值相吻合。该方法操作简单,用微波消解技术大大缩短了样品前处理的时间,用抗坏血酸代替国标方法中的对苯二酚避免了有毒试剂对化验员的危害及环境的污染,重复性好,适于食品中磷元素含量的测定。     

食品中磷测定方法的改进

文章对分光光度法测定食品中磷含量进行改进,根据实验特点,样品经湿法消化后,磷在酸性条件下与钼酸铵结合生成磷钼酸铵,磷钼酸铵被抗坏血酸还原成蓝色化合物——钼蓝,该化合物最大吸收波长为660nm,相关系数r=0.9999,回收率96.8%-100.4%,该方法测定结果与国标的测定结果比较无显著性统计学差别,重现性好,灵敏度高,操作简单方便,大大提高了工作效率,适用于食品中磷的测定。     

Extractable phosphorus related to forms of phosphorus and other soil properties

The soil P extracted by Olsen's, Bray's P-1, Morgan's, North Carolina, 0.01M-CaCl₂, acidic N-ammonium acetate and isotopic-exchange methods of determining available P were related to the forms of soil P and to other soil properties. Correlations between soil tests were higher when both test values were well correlated with a common P form, thereby indicating their similarity in selective dissolution of specific forms. Linear regression equations derived by stepwise inclusion of significant independent variables in order of importance for explanation of variations in soil-test values, indicated that the greatest contribution to Olsen's or Bray's test values was aluminium-P, to the isotopic exchange P was iron-P and to North Carolina test values was calcium-P. Dithionite-extractable aluminium and iron, organic matter, soil texture, base saturation and soil reaction were included in regression equations to reflect their significant influence on the dissolution of specific P forms and secondary reactions occurring during the extraction process. Based on observations for 343 differing soils, regression equations to predict soil-test values from significant P forms and soil properties accounted for more than 50% of variations in P soil-test values for Olsen's, Bray's, North Carolina and 0.01 M-CaCl₂ extraction methods. No improvement was found when P forms were included regardless of significance and significant soil properties were added to the regression equations.     

Utilization of phosphorus in lactating cows fed varying amounts of phosphorus and forage

The objective of this study was to determine the effect of dietary forage proportion and P content on fecal P excretion. Four dietary treatments were formed in a 2 x 2 factorial arrangement. The P content was 0.33 or 0.42%, and the forage proportion was 48 or 58% on a dry matter (DM) basis. The neutral detergent fiber content was 27 and 30% for the low and high forage diets, respectively. The P amount was varied by using monosodium phosphate, and the forage amount by changing the proportions of alfalfa silage and corn. The diets were fed to 44 midlactation Holsteins for 14 wk. Fecal P excretion was estimated using Cr marker and grab sampling. Dietary P content did not affect DM intake, milk yield, or milk composition. The P intake averaged 74 and 96 g/d and fecal P averaged 0.69 and 0.92% (DM basis) or 49 and 65 g/d for the low and high P diets, respectively. Thus, reducing dietary P from 0.42 to 0.33% resulted in approximately 25% less estimated fecal P excretion. Increasing dietary forage reduced milk yield (34.0 vs. 36.5 kg/d), but increased milk fat content (3.66 vs. 3.25%). Estimated apparent digestibility of P tended to decrease (31.1 vs. 36.6%) when the forage proportion increased, but most of the change occurred when the diets contained the low amount of P. Overall, the effect of forage proportion on estimated fecal P excretion was small when diets contained 48 or 58% forage, varied by alfalfa silage. Phosphorus intake has a much larger impact on fecal P excretion than forage proportion, and it does not seem necessary to adjust the dietary P content according to the forage proportion to provide the same amount of absorbed P.     

Bioavailability of phosphorus from defluorinated and dicalcium phosphates and phosphorus requirement of calves

Bioavailability of P from defluorinated phosphate and dicalcium phosphate and the P requirement were studied with 63 male Holstein calves. A P depletion diet containing .08% total P on a dry matter basis was fed to all animals for 4 wk beginning at 6 wk of age and 61 kg weight. Calves developed typical signs of P deficiency. The depletion period was followed by a 6-wk experimental period in which the same depletion diet was used as a control. Phosphorus from each of the two sources was added to make diets containing .14, .20, and .32% total P. Source of supplemental P did not affect weight gains, feed consumption, feed efficiency, serum inorganic P, serum alkaline phosphatase, or bone ash.     

Utilization of phosphorus in lactating cows fed varying amounts of phosphorus and sources of fiber

This study was undertaken to determine the effect of dietary P content and fiber source on P utilization. Four dietary treatments were formed in a 2 × 2 factorial arrangement. The P content was 0.32 or 0.44%, and the fiber source was varied by substituting 10% soyhulls for 6% alfalfa hay on a dry matter (DM) basis. Diets also contained approximately 50% corn silage and alfalfa silage for all treatments. The diets were fed to 32 early to midlactation Holsteins for 10 wk. Fecal P excretion was estimated using indigestible acid detergent fiber marker determined with 12-d in situ incubation and grab sampling. Milk yield was high, averaging 43 kg/d across treatments, and 42.1 and 44.0 kg/d for the 0.32 and 0.44% P diets, respectively. Milk fat content was also high, averaging 3.68 and 4.12% for the 0.32 and 0.44% P diets, respectively. Milk protein yield averaged 1.240 and 1.323 kg/d. Differences in milk production were associated with 1.5 kg/d less DM intake for the lower P diets on average. Based on lactation performance, 0.32% P appeared inadequate for this level of production, whereas the calculated (National Research Council) requirement was 0.37%. Fecal P concentration increased linearly with P intake, and based on this relationship, reducing dietary P from 0.44 to 0.37% would reduce fecal P excretion by 12%. Partial substitution of soyhulls for alfalfa hay did not affect feed intake or milk production, but reduced fecal P excretion, partially because of increased P apparent digestibility. The reduction in fecal P excretion resulting from reduced P intake or substitution of soyhulls for alfalfa hay was apparently through reductions in the regulated portion of fecal P. Cows producing 43 kg/d of milk appeared to need > 0.32% P, whereas the requirement assessed from National Research Council data was 0.37%. Using highly digestible nonforage fiber sources in place of forage fiber sources in the diet may allow less P to be fed while still meeting the requirement.     

Short communication: Effect of abomasal inorganic phosphorus infusion on phosphorus absorption in large intestine,milk production,and phosphorus excretion of dairy cattle

The objective of the study was to evaluate the effect of inorganic phosphorus (Pi) infusion on P absorption in large intestine, milk production, and phosphorus excretion. Four ruminally and ileally cannulated crossbred cows were used in a 4 × 4 Latin square with 21-d periods. Cows were fed a total mixed ration containing 0.21% P, providing 50% of the cows' P requirement. Cobalt-EDTA was used as marker to measure large intestine digesta flow. On d 13 to 21 of each period, each cow was infused daily with 0, 20.1, 40.2, or 60.3 g of Pi into the abomasum and total collection was conducted on d 18 to 21. Ileal samples were collected every 9 h on d 18 to 21. Feed, digesta, and fecal samples were analyzed for total P and Pi using the molybdovanadate yellow method and blue method, respectively. All data were analyzed using PROC GLIMMIX in SAS 9.3 (SAS Institute Inc., Cary, NC) using contrasts to evaluate linear, quadratic, and cubic effects of Pi infusion dose. Dry matter intake, apparent dry matter digestibility, milk yield, and milk total P were unaffected by Pi infusion. Ileal flow and fecal excretion of total P and Pi increased linearly with increasing infused Pi. In the large intestine, net absorption of TP and Pi was increased linearly with increasing infused Pi. The magnitude of absorption from the large intestine was greater than reflected in current models, raising questions that could be evaluated with longer infusion periods or dietary alteration.     

Nitrogen and phosphorus partitioning in lactating Holstein cows fed different sources of dietary protein and phosphorus

To evaluate dietary N and P partitioning, 36 Holstein cows grouped by parity were assigned at calving to diets supplemented with soybean meal (S) or a combination of S and blood meal (B). Diets S and B were formulated to contain 16.2% CP and 0.35% P using mono- and dicalcium phosphate (PM) or wheat bran (WB) as the supplemental source of P. Actual dietary P contents were 0.38, 0.36, 0.34, and 0.34% for SPM, BPM, SWB, and BWB. Two-day total collections of feces, urine, and milk were conducted between 30 and 45 d in milk (DIM), then all cows were fed a control diet until 120 DIM. Between 120 and 150 DIM, cows were again fed the diet assigned at calving, then 2-d total collections of feces, urine, and milk were conducted. Milk production was similar for cows fed diets containing WB (SWB or BWB) when compared with cows fed PM. However, DMI tended to be lower, and P intake and total P excretion were lower in response to WB (20.7 kg/d, 71.9 g/d, and 40.3 g/d) compared with cows fed PM (23.0, 86.7, and 46.8 g/d). Apparent digestibility of dietary P did not differ due to source of supplemental P, averaging 45% across diets. The lower P intake by cows fed WB resulted in lower absorbed P and lower retained P (32.2 and 7.5 g/d) compared with those fed PM (40.6 and 13.4 g/d). Apparent N digestibility, urinary N, and N retention were not affected by P source. Blood meal decreased apparent N digestibility and absorbed N, and also decreased P retention compared with S. In later lactation, cows retained proportionately more absorbed N and P in body tissue and secreted less in milk than they did in early lactation. Results indicated the organic source of P (phytate-P) in WB can be used to provide a substantial portion of the P needed in dairy cattle diets after peak lactation, but the amount of WB in the diet during early lactation should be limited to prevent suppression of DMI and P retention.